1. Field
The present disclosure relates generally to communication systems, and more particularly, to reducing the amount of time for sending a Pilot Strength Measurement Message (PSMM) after sending a completion message during a transfer between a first Radio Access Technology (RAT) and a second RAT in wireless communication.
2. Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
1x Circuit Switched Fallback (1xCSFB) provides a mechanism to support 1x circuit services while a User Equipment (UE) camps on Evolved UMTS Terrestrial Radio Access Network (E-UTRAN). In native 1x, state searches including neighbor searches are performed while a mobile device in is a 1x idle state. Therefore, a UE enters traffic with a neighbor list generated during the 1x idle state, including filtered search results. This allows a head start on the searching that the UE performs in traffic because the UE will have a starting point to prioritize what to search. The UE has a better chance of moving better neighbor pilots into an active neighbor set quickly.
However, in Enhanced 1xCSFB (e1xCSFB), the Universal Handoff Direction Message (UHDM) will direct the UE to transfer from E-UTRAN into 1x traffic without neighbors. This increases the chance of fast call drops for the UE. After a 1x neighbor list is received, the UE will require additional time to build up multiple measurements in an algorithmic fashion to determine whether to report neighbors identified on the neighbor list. These measurements must be built and made before the UE sends a PSMM and begins the process of moving a neighbor pilot into the active neighbor set. In highly dynamic environments, this added delay can cause a large number of dropped calls due to a lack of neighbors in the active set.
Therefore, a mechanism is needed for reducing the amount of fast call drops during a transfer from a first RAT to a second RAT.